Presently disclosed embodiments are directed toward methods and systems for compensating spot color emulation colorant recipes for changes in performance, or drifts, in an associated color producing system or process.
In color producing systems or processes, such as, color printers, copiers, display devices, and the like, most requests for the production of colors are processed through a system profile. For example, the system profile includes a calibration curve or curves for transforming color descriptions of requested colors into colorant recipes based on the performance of the color producing system at the time of the system's most recent calibration. For instance, the system profile may provide information for transforming a requested color description in terms of an industry standard machine independent color space, such as that known as CIE1976 (L*a*b*) or CIELAB (of the Commission Internationale d'Eclairage), which describe color in terms of 3 parameters, known as L*, a*, b*, into colorant amounts. For example, many color producing systems produce colors by applying varying amounts of cyan, magenta, yellow and black colorants (e.g., inks or toners) to a print medium (e.g., vellum or paper). Other color producing systems may employ additional colorants, such as orange, green, violet, light cyan, light magenta, and/or grey. Some color producing systems (e.g., display devices) produce colors by presenting various intensities of colored light (commonly red, green and blue). Colors produced through this transformation process are referred to as “process colors”.
Generally, imperfections in the system profile, which may lead to small errors in the accuracy of the rendered color, are tolerable in the rendering of process colors.
Colors which are of particular importance to document or image authors are referred to as “spot colors”. Spot colors can include colors associated with a company's logo, trademark or trade dress. Additionally, spot colors may be used when color accuracy is particularly important, such as when printing catalogs of clothing or decorative items or paint color selection guides.
Color producing systems that support the emulation of spot colors often include spot color tables, which associate spot colors, either by name or identification information, with a colorant recipe. Additionally, spot colors can be defined by parameter values in one or more industry standard machine independent color space (e.g., L*, a*, b*).
Traditionally, spot color tables have been generated manually through a process of trial, visual evaluation and adjustment. Since there are many spot colors in a table (over 1,000 in some cases), the generation and updating of a spot color table can be time consuming and expensive.
Recently, the inclusion of inline (in situ) spectrophotometers in high-end color producing systems has allowed the creation and maintenance of spot color tables to be at least semi-automated. However, the iterative trial and error process can still consume many sheets of print media, inks and/or toners (where the color producing system involves printing) as well as time.
Color producing systems can drift with time. Display elements age and change in efficiency. The characteristics of toners and inks vary with manufacture, production lot, time, temperature, humidity and age. Accordingly, a spot color table prepared at a first point in time can prove to be inaccurate if used to produce spot colors at a second point in time. Spot color tables can be updated by recalibration at such a second point in time. However, as indicated above, such recalibrations are time consuming and wasteful of material.
Therefore, there is a need for methods and systems for updating or compensating spot color tables for drift in associated color producing systems that minimize the use of consumables and time devoted to the compensating or updating process.